Method and device for propulsion of vessels

ABSTRACT

A method for propulsion of water-going vessels ( 1 ) comprising a plate ( 9 ), which is located in the water ( 2 ) and extends across a desired direction of motion for the vessel ( 1 ), where the plate ( 9 ) is moved from a first position (P 1 ) to a second position (P 2 ) and back. Under the influence of a motive force the extent of which varies sinusoidally, the plate ( 9 ) is brought into translatory and rectilinear oscillation about a neutral position (N 2 ) between the first and the second position (P 1  and P 2  respectively), the neutral position (N 2 ) being determined by a static equilibrium between spring forces influencing the plate ( 9 ). The plate ( 9 ) is controlled in such a manner that its plate plane extends perpendicularly to the vessel&#39;s ( 1 ) direction of motion, and a greater resistance is exerted by the plate ( 9 ) against the water when it is moved opposite to the vessel&#39;s desired direction of motion than when it is moved in this direction. A device for performing the method.

CROSS-REFERENCE TO RELATED APPLICATIONS

Statement Regarding Federally Sponsored Research or DevelopmentReference to a “Microfiche Appendix”

BACKGROUND OF THE INVENTION

The invention relates to a method for propulsion of water-going vesselsby means of a body which can be moved forward and backward relative tothe vessels hull and which has a propulsion portion which is located inthe water, a drive device which is arranged to move the body in a firstdirection, and a first resiliently elastic device or spring device whichis arranged to exert spring forces against and move the body in asecond, opposite direction, the propulsion portion's water resistancebeing greater when it is moved opposite a desired propulsion directionfor the vessel than when it is moved in this propulsion direction.

The invention also relates to a device for performing the method.

In FR-A-2 446 220 there is disclosed a device of this type, However,there is no suggestion as to second spring means acting in the activedirection of the propelling body such as to form an oscillating systemwith the propelling body and the first spring means in two directionsabout a neutral position and to provide for sinusoidal variation of themotive power.

In known types of mechanical propulsion of vessels where a body is movedin water which surrounds the vessel in order to provide a flow of waterin a direction which is oppositely directed to the desired motion of thevessel, the body is rotated. Thereby relative movements of the water andthe body are created and associated components of the force which areexerted by the water on the body, where some of these components do notcontribute of the propulsion of the vessel. This is the case, e.g., inpropeller propulsion as well as paddle wheel propulsion.

For propulsion of this kind where a mass of water m with a velocity v,e.g., is thrust backwards from a vessel per time unit, a reaction forceF=m ·v is obtained. Since the space available for a propeller behind avessel is limited, and the propeller only partly utilises this space, arelatively high velocity v must be selected in order to achieve anacceptable thrust. This results in a substantial power loss as a resultof propeller resistance, eddying, etc., in addition to possiblecavitation.

BRIEF SUMMARY OF THE INVENTION

The object of the invention is to provide a method and a device of thetype mentioned in the introduction, which is not encumbered by thesedisadvantages.

The characteristics of the method and the device are described brieflyas follows.

A method for propulsion of water-going vessels by means of a body (8, 9,10) which can be moved forward and backward relative to the vessel'shull in accordance with the principles of the claimed invention has apropulsion portion (9) which is located in the water (2), a drive device(4) which is arranged to move the body (8, 9, 10) in a first direction,and a first resiliently elastic device or spring device (11) which isarranged to exert spring forces against and move the body (8, 9, 10) ina second, opposite direction. The propulsion portion's (9) waterresistance is greater when it is moved opposite a desired propulsiondirection for the vessel than when it is moved in this propulsiondirection.

The body (8, 9, 10) is influenced by further spring forces which areexerted in the first direction. The amount of motive power is variedsinusoidally. The spring force-influenced body (8, 9, 10) is broughtinto translatory and rectilinear oscillation with a natural frequency(E) in the two directions about a neutral position (N2), the neutralposition (N2) being determined by a static equilibrium between thespring forces influencing the body (8, 9, 10).

A device for propulsion of water-going vessels by means of a body (8, 9,10) which can be moved forward and backward relative to the vessel'shull in accordance with the principles of the claimed invention has apropulsion portion (9) which is located in the water (2), a drive device(4)which is arranged to move the body (8, 9, 10) in a first direction,and a first resiliently elastic device or spring device (11) which isarranged to move the body. (8,9,10) in a second, opposite direction. Thepropulsion portion's (9) water resistance being greater When it is movedopposite a desired propulsion direction for vessel than when it is movedin this propulsion direction.

The device comprises a second resiliently elastic device or springdevice (12) which is arranged to move the body (8, 9, 10) in the firstdirection. The spring devices (11,12) and the body (8, 9, 10)forin-an-oscillating device with a natural frequency (E). The drivedevice (4) is arranged to provide the oscillating device with sufficientenergy to bring the body (8, 9, 10) into oscillation with a naturalfrequency (E) and with a desired amplitude.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention will now be described in more detail with reference to thedrawing which schematically illustrates an embodiment of a deviceaccording to the invention.

FIG. 1 is a side view of a vessel with a propellant device according tothe invention, where portions of the vessel's hull have been cut away.

FIG. 2 is a graph illustrating a sinusoidal, time-dependent, dampedmovement of a plate.

It should be understood that the vessel's bow faces the left-hand edgeof the drawing and that this direction should be. designated as“forward”.

DETAILED DESCRIPTION OF THE INVENTION

As is schematically illustrated in FIG. 1, a vessel 1 is floating inwater 2 with a surface 3. The vessel has a motor 4 which has a drivingrod 5, which can be moved forward and backward along the vessel'slongitudinal direction, as indicated by the double arrow A1. The rearportion of the driving rod S is fixedly connected to a drive flange 6. Acentral or neutral position for the rear end of the drive flange 6 isindicated by N1 in the figure. Sealingly through the vessel's stenpost 7there extends in the vessel's longitudinal direction a supporting rod 8,which is mounted in a bearing device (not shown), thus enabling thesupporting rod 8 to be moved freely forward and backward linearlytranslatorily in this direction as indicated by the double arrow A2.

The rear end portion of the supporting rod 8 is fixedly connected to aplate-shaped water-influencing device, hereinafter called a plate 9,whose plate plane extends substantially perpendicularly to thesupporting rod's longitudinal direction. The plate's height and widthmay correspond to the vessel's draught and width respectively. It willbe understood, however, that the plate may project below the vessel'sbottom 8 and be higher or lower than the vessel's draught, and be wideror narrower than the vessel's width. For forward propulsion of thevessel, the plate is formed in such a manner that it exerts asubstantial. water resistance when it is moved backwards, but only aminimal water resistance when it is moved forwards. More precisely theplate can be designed in such a manner that water from the front side ofthe plate easily reaches the rear side of the plate when the plate ismoved forwards, and that water from the rear side of the plate issubstantially prevented from reaching the front side of the plate whenthe plate is moved backwards.

The supporting rod's front end portion is fixedly connected to asupporting rod flange 10 which extends across the supporting rod'slongitudinal direction.

Between the vessel's sternpost 7 and the supporting rod flange 10 thereis arranged a first compression spring device 11 which attempts to movethe supporting rod 8 and thereby the plate 9 forwards. Similarly betweenthe drive flange 6 and the supporting rod flange 10 there is arranged asecond compression spring device 12 which attempts to move thesupporting rod 8 and thereby the plate 9 backwards. In the drawing thesespring devices 11, 12 are hereinafter called springs, symbolicallyillustrated as helical springs, although other suitable types of springsor spring devices may be employed. When the springs 11, 12 are at rest,i.e. in static equilibrium, and the drive flange 6 is located in itsneutral position, the plate 9 is located in a central or neutralposition as indicated by N2 in the figure.

During operation the motor 4 moves the driving rod S and the driveflange 6 in an oscillating manner, preferably sinusoidallytime-dependently, about the first neutral position N1 as indicated bythe arrows A3. The amplitude may be adjustable.

If the drive flange 6 is initially moved forward when the motor 4 isstarted, the second spring 12 is expanded. Thus this spring then exertsa reduced force against the supporting rod flange 10. The staticequilibrium between the springs 11, 12 is thereby upset and the firstspring 11 is also expanded, thus causing the supporting rod 8 and theplate 9 to be moved forward from the neutral position to a firstposition P1, downstream relative to the neutral position N2 and thevessel's forward direction.

When the drive flange 6 is then moved backwards, the second compressionspring 12 is compressed to an increasing extent, exerting an increasedforce on the supporting rod flange 10. The first compression spring 11is thereby compressed, with the result that the plate 9 is movedbackwards, past the neutral position N2 to a second position P2,upstream relative to the neutral position N2.

The mass of the supporting rod 8, the plate 9 and the supporting rodflange 10 together with the springs 11, 12 form an oscillating device.An oscillation of this device is damped by, amongst other things, thewater influence of the plate 9 and the device has a natural frequency E.

FIG. 2 is a general illustration of a graph in which along a verticalaxis is indicated the distance s from a neutral position for a freelyoscillating object during two successive oscillations, and the time t isindicated along the other axis, the oscillatory motion being damped,i.e. the amplitude of the last oscillation has been reduced by adecrement D relative to the amplitude of the previous oscillation.

To prevent a reduction in the plate's amplitude during the course of anoscillation, for each oscillation the motor must provide the oscillatingdevice with an output via the driving rod 5 according to the dampeddevice's amplitude decrement.

For example, the oscillating device's frequency may be 50 Hz, but thisfrequency naturally depends on the device's size, design and otheroperating conditions.

By means of this propulsion device an enormous mass of water can bemoved. Thus, in order to achieve the desired motive power for thevessel, the water moved can have a low velocity. Furthermore, a very lowlevel of noise is emitted by the device during operation. The totalefficiency of the vessel's propulsion device can thereby be substantial.

The danger which a rotating propeller represents for objects in thewater is avoided with the device according to the invention.

It will be appreciated that the plate can generate a movement of thevessel in a desired direction, depending on the plate's direction ofmotion and that the term propulsion should be understood as a movementof the vessel in this direction. Moreover, it will be understood thatmore than one plate may be employed.

What is claimed is:
 1. A method for propulsion of water-going vessels,comprising the steps of: arranging a body that is movable forward andbackward relative to a hull of the vessel, the body comprisingpropulsion portion located in water, a rod extending in a longitudinaldirection of the vessel and sealingly through a sternpost of the vessel,a rear end portion of the rod being fixedly connected to the propulsionportion and, a flange extending transversely relative to the rod, andfixedly connected to a front end portion of the rod, arranging a drivedevice so as to move the body in a first direction, the drive devicecomprising a drive element, arranging a first resiliently elastic devicecomprising a first spring between the flange and a fixed portion of thehull so as to exert spring forces against and move the body in a seconddirection opposite the first direction direction, a water resistance ofthe propulsion portion being greater when the propulsion portion ismoved opposite a desired propulsion direction for the vessel than whenthe propulsion portion is moved in the desired propulsion direction,arranging a second resiliently elastic device comprising a second springon an opposite side of the flange from the first resiliently elasticdevice, between the flange and the drive exerting further spring forceson the body in the first direction, and varying an amount of motivepower sinusoidally, so as to bring the body into translatory andrectilinear oscillation with a natural frequency (E) in the first andsecond directions about a neutral position, the neutral position beingdetermined by a static equilibrium between the spring forces influencingthe body.
 2. A method according to claim 1, further comprising the stepof providing the body with sufficient energy via the drive device tocompensate for an amplitude decrement for the body.
 3. A methodaccording to claim 1, further comprising the step of adapting the springforces to a mass of the body, such that the natural frequency isapproximately 50 Hz.
 4. A method according to claim 1, furthercomprising the step of providing the body with energy impulses with afrequency corresponding to the natural frequency.
 5. A device forpropulsion of water-going vessels, comprising a body that is movableforward and backward relative to a hull of the vessel, the bodycomprising a propulsion portion located in the water, a rod extending ina longitudinal direction of the vessel and sealingly through a sternpostof the vessel, a rear end portion of the rod being fixedly connected tothe propulsion portion and, a flange extending transversely relative tothe rod, and fixedly connected to a front end portion of the rod, adrive device adapted to move the body in a first direction, the drivedevice comprising a drive element, a first resiliently elastic devicecomprising a first spring disposed between the flange and a fixedportion of the hull so as to move the body (8, 9, 10) in a seconddirection opposite the first direction, a water resistance of thepropulsion portion being greater when the propulsion portion is movedopposite a desired propulsion direction for the vessel than when thepropulsion portion is moved in the desired propulsion direction, asecond resiliently elastic device comprising a second spring disposed onan opposite side of the flange from the first resiliently elasticdevice, between the flange and the drive element, arranged to move thebody in the first direction, wherein the first and second spring elasticdevices and the body form an oscillating device with a naturalfrequency, and wherein the drive device is arranged to provide theoscillating device with sufficient energy to bring the body intooscillation with the natural frequency and with a desired amplitude. 6.A device according to claim 5, wherein the drive device is adapted toprovide the body with sufficient energy to compensate for an amplitudedecrement of the body.
 7. A device according to claim 6, wherein thedrive device is adapted to provide the body with energy impulses with afrequency corresponding to the natural frequency.
 8. A device accordingto claim 5, wherein the natural frequency is approximately 50 Hz.